Move shaders into glsl and hlsl directories

Move `data/shaders` to `data/shaders/glsl`
Move `data/hlsl` to `data/shaders/hlsl`

Fix up shader paths in the cpp files to point to the new glsl location.

`data/shaders/hlsl/compile.py` still overwrites the glsl .spv files (for
now).

Issue: #723

data/shaders/glsl/deferredshadows/shadow.vert

@@ -0,0 +1,11 @@
+#version 450
+
+layout (location = 0) in vec4 inPos;
+
+layout (location = 0) out int outInstanceIndex;
+
+void main()
+{
+	outInstanceIndex = gl_InstanceIndex;
+	gl_Position = inPos;
+}